DESCRIPTION: (adapted from the abstract) This proposal will examine the effects of various vasoactive agents (alpha1 and alpha2 adrenergic, angiotensin, serotonin, beta adrenergic and other compounds that alter cyclic AMP) on the activity of the Na/K pump in canine vascular smooth muscle. Specifically, studies will determine whether these agents activate the pump indirectly by increasing ion availability and/or directly by modifying pump function. To examine these possibilities, the investigator will employ a variety of experimental approaches and preparations. Studies on intact tissues will examine the effects of agonists on pump function, Na contents and cyclic AMP levels. Studies on membrane fractions will investigate cyclic AMP dependent changes in Na/H or Na/Ca exchange that could secondarily affect Na/K pump activity. Molecular biological approaches will examine mRNAs for the a and b subunits of the Na/K pump and define their content and will use PCR to produce a cDNA probe for screening vascular smooth muscle (VSM) libraries to identify the two mRNAs that appear to code for the a subunit and other possible subunit isoforms.